Ships with Wärtsilä’s Airguard and Oceanguard propellor shaft seals have no need to change from mineral oil to a bio-degradable lubricant (formally ‘an Environmentally Acceptable Lubricant’) when they're in U.S. waters as these seals meet Vessel General Permit (VGP) requirements. How these particular propeller shaft seals comply, and more about these newish VGP amended regulations follows:Seals,bearings and stern tube arrangement: Image courtesy of WärtsiläNo oil-to-sea interfaceWärtsilä explain that Airguard is suited for merchant ship stern tube and thrusters, and Oceanguard for cruise, ferry and offshore stern tube, thruster and electric pod face type sealing. The Airguard and Oceanguard sealing systems have been designed with no oil-to-sea interface (the essential point): an air chamber or separation space within the seal captures any water or oil leakage, which is then transferred to inboard tanks for monitoring and further tre... [More]